The prevalence and incidence of obesity is a serious threat to public health in the United States, and has reached epidemic proportions. Additional concerns are the associations of overweight and obesity with cardiovascular disease, diabetes, cancer, and other debilitating conditions. This proposed project responds to the call for efforts to identify and measure potential causal associations between the built environment and obesity, and related comorbidities. This investigation proposes a longitudinal, multilevel project to examine how the physical and built environment may influence levels of overweight and obesity, physical inactivity, and blood pressure in neighborhoods of older residents. The primary aims are to: (a) simultaneously examine neighborhood- and resident-level change in body mass index, physical activity, and blood pressure over a three-year period, and (b) identify neighborhood-level physical and built environment correlates of change in the proposed outcomes while controlling for covariates at the resident-level. Using a multistage sampling design, the study will recruit 1,800 community residents aged 60 years and older from a random sample of 120 census-block groups (defined as a proxy for neighborhoods - the primary sampling unit) in Multinomial County, Oregon. Data to be gathered include surveys, assessments, census and Geographic Information Systems data, and dependent outcome measures of body mass index, physical activity, and blood pressure. Key physical and built environment measures will include hilly terrain, urban form, and density of fast-food restaurants. The resulting environmental and personal factors data will be integrated into a three-level statistical model involving temporal measures (Level 1), that are nested within residents (Level 2), who are themselves nested within neighborhoods (Level 3). The hierarchically structured data, to be analyzed through multilevel modeling methodologies, will examine both inter-neighborhood and inter-resident variability in change in the proposed outcomes, as well as the degree to which neighborhood-level built environment variables are related to variation in change in the outcomes over time. This proposed investigation extends the current individual oriented paradigm to an ecological, multilevel paradigm for assessing the extent to which built environment factors influence obesity and obesity-related outcomes over time in the neighborhoods of older adults. The results of this study are likely to increase understanding of the unique influences of physical and built environment factors which directly and indirectly affect neighborhood-level overweight and obesity in older adults, and will provide information to guide future pubic health investigations to slow the pace of this growing epidemic.